Need tips on how to get S game on supports

Just carried a game with support blitzcrank. We stomped our lane early so I bought a snowball ring. Went 8/2/8, some of them solo kills on their jinx, expecting to get my second S game for grade 7 (got my first one over a year ago) but, nope. Not even close actually. Got an A- instead.

I mean like, that's 5 grades lower than I expected. I know it has a lot to do with warding and clearing theirs, but I placed by far the most wards of the game and didn't clear any because their team barely warded (I don't think they placed a single ward after I got lvl 9 because everyone that left the turret got hooked and killed).

I also have a feeling that you get punished for not building the standard items. I didn't get redemption so I couldn't heal my team. If that's a requirement to get high grade, then that's bullshit. Also probably should've farmed more. Everyone knows Blitz is supposed to always use his R on minion waves to steal cs. Those are the true supports, I suppose.

(for the record, my adc obviously did get an S, 'cause hey, he totally outfarmed their adc. Has nothing to do with theirs being zoned by the suport or something.)

http://matchhistory.euw.leagueoflegends.com/en/#match-details/EUW1/3144273312/36603236?tab=overview